IRMAA Two-Year Lookback: Which Tax Year Does Medicare Use?

IRMAA and your tax return

For 2026 Medicare premiums, Social Security normally uses your 2024 tax return. For 2027, it will generally use your 2025 return. This two-year lookback applies to income-related monthly adjustment amounts (IRMAA) for Medicare Part B and Part D. A missing return, corrected IRS data, or a qualifying life-changing event can change the determination.

Last checked against SSA regulations, CMS premium tables and IRS forms: October 17, 2026. All 2027 premium references are forward-looking; official 2027 brackets were not yet available on that date.

That two-year gap is why IRMAA so often shows up at an awkward moment. A last full year of salary, a large Roth conversion, the stock you sold to pay for a new roof: each one reaches your Medicare bill two years after the money did, when your life may look nothing like the return Social Security is reading.

Below, you'll see which return lines up with which premium year, how to confirm the year on your own notice, when Social Security uses a different year, and what you can still influence.

The tax year two years before the premium year. The federal regulation says Social Security will generally use the modified adjusted gross income the IRS provides for the tax year two years before the year the adjustment takes effect (20 CFR 418.1135). For 2026 premiums, Social Security's own example is a return filed in 2025 for tax year 2024 (SSA).

Three terms keep it straight:

Premium year

The calendar year you pay the surcharge. IRMAA is decided one year at a time, and Social Security's annual letter says the amounts apply to that year only.

Lookback year

The tax year whose income is being measured, normally two years earlier. Income you earn in 2026 belongs to the 2028 premium year.

MAGI

What Social Security measures from that return: adjusted gross income plus tax-exempt interest. It isn't the same as taxable income.

It also helps to know who does what. CMS publishes the premiums and income brackets each year. Social Security applies them to the figures it gets from the IRS and sends the IRMAA letter. Questions about which year or which income was used go to Social Security; mistakes in the income itself get fixed with the IRS.

IRMAA is not an extra tax on everyone with Medicare. It applies only when the relevant income threshold is exceeded and the person has coverage subject to the adjustment. People in Medicare Advantage can still owe Part B IRMAA and, if their coverage includes Part D, Part D IRMAA. If you have only one of those coverages, you pay an adjustment only for the coverage you have (SSA).

Why two years, and not last year?

Because of when premiums are set. Next year's amounts are worked out late in the year before, and at that point the most recent complete return the IRS has for most people is from the year before last. Social Security's operations manual explains the lookback exactly this way (POMS HI 01101.030), and its annual IRMAA letter normally goes out late in the year alongside the cost-of-living notice (POMS HI 01194.005).

So right now, in October 2026, Social Security is preparing 2027 premiums. The newest full return it can get for most people is 2025.

"Most recent return" and "two years ago" are usually the same return

Social Security also describes its rule as using "the most recent federal tax return the IRS provides" to it. That sounds like a contradiction. It isn't. At the moment premiums are set, the most recent return and the two-year-old return are normally one and the same.

The confusion often starts after you file another return. Filing your lower 2025 return in April 2026 does not automatically recalculate 2026 premiums that were determined using 2024. Social Security generally considers that 2025 return for 2027 premiums. If the 2024 information was unavailable or wrong, or you qualify for a more recent-income determination after a listed life-changing event, a separate correction procedure may apply (20 CFR 418.1310).

The timing matters most around retirement. Consider this hypothetical: you are single, already on Medicare, and retire on June 30, 2026. Here is how your earlier salary could still appear in later premium calculations.

1. 2026 premiums use your 2024 returnA full year of salary.
2. 2027 premiums use your 2025 returnAnother full year of salary.
3. 2028 premiums use your 2026 returnSix months of salary, plus whatever retirement income started in July.
4. 2029 premiums use your 2027 returnYour first year with no wages at all.

Under the normal rule, both 2026 and 2027 premiums reflect full working years, and 2028 premiums reflect the year you worked for six months. That does not mean you must keep paying IRMAA at those levels. Retirement may qualify you to request a determination based on lower, more recent income.

This is the gap Form SSA-44 was built for. Stopping work is one of the listed life-changing events, and if it drops your more recent income far enough to change your bracket, you can ask Social Security to use the newer year instead (20 CFR 418.1205; 418.1215). Our guide to which year to put on Form SSA-44 after retiring walks through that choice.

Approaching 65? Your first premium year usually looks back to age 63

For someone who first enrolls in Medicare at 65, the first premium year usually uses the tax year in which they turned 63. For example, turning 65 and enrolling in 2028 generally means Social Security looks at the 2026 return. Enrollment can begin earlier or later for some beneficiaries, and the rule depends on the premium year, not a particular birthday.

If you delay Part B enrollment, for example because you have qualifying coverage through current employment, the usual income lookback still counts backward from the calendar year when premiums apply. Separate Medicare enrollment rules and deadlines apply to delaying coverage.

New enrollees sometimes see the result arrive out of order. Until the IRS figures come back, Social Security charges the standard Part B premium and no Part D IRMAA, then applies any surcharge retroactively (POMS HI 01101.030). A first year that starts at the standard premium and later picks up back charges may simply be the lookback catching up.

Three items: your filing status, your adjusted gross income (AGI) and your tax-exempt interest. Social Security adds the last two together and calls the result modified adjusted gross income, or MAGI (SSA).

Form 1040 line numbering changed for 2025: AGI appears at line 11a on page 1 and is carried to line 11b on page 2. The 2024 form uses line 11. In both years, tax-exempt interest is on line 2a. The 2026 SSA-44 instructions still describe the older line-11 layout; use the line for AGI on the return you actually filed.

For IRMAA, AGI is the starting point, not taxable income. Standard or itemized deductions and the 2025 Schedule 1-A deductions (including the additional deduction for eligible older taxpayers) are taken after AGI and therefore do not directly reduce IRMAA MAGI. By contrast, tax items that legitimately reduce AGI can reduce the amount used for IRMAA (2025 Form 1040).

Municipal bond interest works the other way. It's tax-exempt on your return, and Social Security adds it back.

Common reasons for higher MAGI include wages or bonuses, taxable traditional IRA withdrawals, required minimum distributions, Roth conversions, taxable capital gains, and net taxable rental or business income. A home sale does not automatically raise MAGI: only a taxable gain that enters AGI matters, after any applicable home-sale exclusion. A qualified Roth IRA distribution ordinarily does not enter AGI (IRS). See our MAGI calculation guide for the line-by-line approach.

There are two different questions: Did Social Security use the correct old return? And does a qualifying event allow it to use newer income? The correct path depends on the reason for the mismatch.

Sources: 20 CFR 418.1135, 418.1150 and 418.1310; Social Security's higher-income premium rules; Form SSA-44.

The three-year-old return is a placeholder

Row one surprises people. If the IRS didn't have your two-year-old return when Social Security asked, for example because you hadn't filed it yet, Social Security can use the return from three years back for now. The rule treats that as temporary: once the two-year-old figures arrive, Social Security recalculates the affected months (20 CFR 418.1135(b)).

A temporary three-year-old return can lead to a higher or lower adjustment when the IRS supplies the two-year-old return. Ask Social Security about any back charges or refunds reflected on your updated notice.

If your notice names the three-year-old year and you've since filed the newer return, Social Security asks you to call or visit so it can update its records. You can request the new decision from the date of the notice through the end of the premium year, or until March 31 of the following year if the notice arrived in October, November or December (20 CFR 418.1310(a)(1)). Social Security's notices also say it won't use tax information more than three years old.

What doesn't change the year

• Your income simply fell. Without one of the listed life-changing events, lower income isn't grounds for a new decision. Social Security's notice uses one-time capital gains as its example of a change it can't act on.
• The spike came from a Roth conversion, a home sale or other one-time income. Those raise MAGI. They aren't life-changing events (20 CFR 418.1205).
• Ordinary market losses or higher living expenses. A routine investment decline is not a qualifying SSA-44 life-changing event. But deductible capital losses and allowable business expenses can affect AGI under IRS rules. Whether a loss changes MAGI is a different question from whether it qualifies for a more recent-year decision. The listed property-loss event generally requires a loss beyond your control (SSA-44 instructions, page 5).
• A qualifying event that leaves you in the same bracket. The drop has to lower or eliminate your IRMAA to count (20 CFR 418.1215).

Your IRMAA determination notice should identify the tax year and the IRS filing status and income figures used. The SSA sample notice is helpful, although exact wording and layout vary by notice type.

1. Find the year. Look for wording such as "based on your 2024 income tax return."
2. Pull that year's Form 1040. Add AGI (line 11, or line 11a on a 2025 return) to tax-exempt interest (line 2a). An IRS transcript works if you can't find your copy.
3. Compare. Check your total and your filing status against the notice. A mismatch is a data problem (rows two and three above), not a life-changing-event problem.
4. Check the year itself. Three years back instead of two means row one applies.
5. Use the right table. Measure that MAGI against the premium year's brackets. 2024 income is judged against the 2026 table, not anything published in 2024.
6. Look forward. Ask whether a listed event since then has cut your income enough to move you down at least one bracket.

If Social Security applied the rules incorrectly and you disagree with its decision, the formal path is a request for reconsideration, not an SSA-44 life-event request. You can appeal online through Social Security or use Form SSA-561-U2. Generally, you have 60 days after receiving the determination notice to request reconsideration; SSA normally presumes it arrived five days after its date unless you show otherwise. If you are late, ask whether good cause can be considered (SSA appeals procedure).

These are the 2026 figures for people with full Part B coverage, using 2024 MAGI (CMS). The Part B column is the total monthly Part B premium, including IRMAA, not just the surcharge. Part D IRMAA is added to your separate prescription drug plan premium. CMS publishes a different Part B table for people with immunosuppressive-drug coverage only.

"Individual return" covers single, head of household and qualifying surviving spouse filers, plus married people who filed separately and lived apart from their spouse all year. Source: CMS 2026 fact sheet and Form SSA-44.

If you filed married filing separately and lived with your spouse at any point during the tax year, the individual/joint table above does not apply. For 2026, the separate scale is:

One dollar over the line

IRMAA brackets have a sharp threshold. Even $1 over an income limit can put you in the next surcharge tier for months covered by that determination, rather than charging a percentage only on the excess dollar. Later corrections or a qualifying event can change the result. Consider two hypothetical single filers with 2024 MAGI only $600 apart.

In this hypothetical, the additional $600 of MAGI corresponds to $144.70 more IRMAA per month ($240.40 − $95.70). If both people had Part B and Part D for all 12 months and no adjustment were later approved, that is $1,736.40 more in surcharges over 2026. Their drug-plan premiums are excluded.

On a joint return, Social Security compares your combined MAGI with the joint brackets, and each spouse enrolled in Part B or Part D pays the surcharge for the coverage they have. That's straightforward when you start Medicare together. When you don't, the lookback can take a decision made while only one of you was enrolled and bill it to both.

The conversion happened the year your spouse turned 63, and it reaches both of you. It isn't a life-changing event, so Form SSA-44 can't undo it. None of this makes the conversion a mistake. It makes the size of the conversion a Medicare decision as well as a tax one, and the time to weigh that is before December 31 of the lookback year, not after the letter arrives.

Widowhood runs the other way. The lookback return may be a joint return that includes a late spouse's income, while your income now is lower and you file as single. A spouse's death is on the list of life-changing events (20 CFR 418.1205), which is the route to asking Social Security to use a newer year.

The standard lookback is predictable, but a correction or life-changing event can change which figures Social Security uses. As of October 2026, the practical options differ by premium year:

2026 premiums (2024 income)

The income is history, so only the exceptions above can change this year's surcharge. If a listed event cut your income this year, the clock matters. Social Security's notice says a drop that happened January through September has to be reported before the end of the year to fix that year's IRMAA; for an event on October 1 or later, you have until the end of March. A favorable decision is generally effective January 1 of the year you ask (20 CFR 418.1230).

2027 premiums (2025 income)

Also settled, because 2025 is over. Watch for your letter late this year and check which year it names. If 2025 still carried a salary and you've since stopped working or had another listed event, you're in SSA-44 territory, and the retirement guide linked earlier covers which year to enter on the form.

2028 premiums (2026 income)

Your 2026 income year is still open until December 31, 2026. Taxable Roth conversions, realized gains and extra taxable IRA withdrawals in 2026 can affect 2028 IRMAA under the normal lookback. 2028 thresholds are not yet known; don’t use 2026 brackets as a guaranteed target when planning transactions. Review taxes and Medicare effects with a qualified professional before making irrevocable decisions.

The calendar explains why the bill looks the way it does. Changing it comes down to a narrower question: did a qualifying life-changing event push your more recent MAGI into a lower bracket? A two-year-old return that no longer matches your life isn't enough on its own. Neither is retiring, if your newer income still lands in the same bracket.

Does Medicare use last year's tax return for IRMAA?

Generally not. Premiums are set late in the year before the premium year, when the latest complete return is usually two years old. Last year's return comes into play when a listed life-changing event lets you ask Social Security to use a more recent year.

Which tax return is used for 2027 IRMAA?

Your 2025 return, under the normal two-year lookback. If the IRS doesn't have it when Social Security asks, Social Security can use 2024 temporarily and correct the amount once 2025 arrives. CMS had not published the 2027 premiums or brackets as of October 17, 2026.

I filed my 2025 return on extension. Which year will Social Security use?

If the IRS had your 2025 figures when Social Security requested them, 2025. If it didn't, Social Security can use 2024 for now and recalculate later, up or down. Check the year your notice names, and if it says 2024, you can give Social Security a signed copy or transcript of your 2025 return.

Does the two-year lookback apply to Part D IRMAA too?

Yes. Part B and Part D IRMAA come from the same MAGI and the same tax year. The Part D amount is deducted from your Social Security benefit or paid directly to Medicare, no matter how you pay your drug plan's premium (CMS).

Can I ask Social Security to use my current income?

Only if one of the listed events caused a drop big enough to lower or eliminate your IRMAA. The list is marriage; divorce or annulment; a spouse's death; you or your spouse stopping or reducing work; certain losses of income-producing property; the loss of pension income from an employer plan's scheduled cessation, termination or reorganization; and an employer settlement payment. Income that fell for other reasons doesn't qualify.

Does a one-time income spike raise IRMAA for more than one year?

A one-time taxable income spike generally affects the premium year two years later, rather than creating a permanent surcharge. If similar income happens in consecutive tax years, it can affect consecutive premium years. SSA recalculates IRMAA for each premium year, and corrections or life-changing-event decisions may alter an initial determination.

Is IRMAA based on my income in the year I turn 65?

Not generally. For someone who starts Medicare at 65, the usual two-year lookback points to the tax year they turned 63. People who enroll at a different age or in another year should count back two calendar years from the premium year.

• Social Security Administration, Premiums: Rules for Higher-Income Beneficiaries (which return is used, MAGI definition, amended returns, life-changing events)
• Social Security Administration, Request to lower an Income-Related Monthly Adjustment Amount (IRMAA)
• Social Security Administration, Form SSA-44, Medicare Income-Related Monthly Adjustment Amount – Life-Changing Event (12-2025)
• Social Security Administration, Form SSA-561-U2, Request for Reconsideration
• 20 CFR 418.1135 (which tax year is used), 418.1150 (amended returns), 418.1205 (life-changing events), 418.1215 (significant reduction), 418.1230 (effective dates), 418.1310 (new initial determinations)
• Social Security Program Operations Manual System, HI 01101.030, IRMAA Determination Process
• Social Security Program Operations Manual System, HI 01194.005, annual IRMAA notice
• Centers for Medicare & Medicaid Services, 2026 Medicare Parts A & B Premiums and Deductibles (November 14, 2025)
• Centers for Medicare & Medicaid Services, 2025 Medicare Parts A & B Premiums and Deductibles (November 8, 2024)
• Internal Revenue Service, Form 1040 (2025)
• Internal Revenue Service, Roth IRAs
• Social Security Program Operations Manual System, HI 01140.001, IRMAA appeals and 60-day reconsideration deadline

CheckIRMAA is independent of the Social Security Administration, CMS and Medicare, and this is not a government website. This article explains federal rules in general terms. It isn't legal, tax or benefits advice, and it can't predict how Social Security will decide a particular request. For decisions such as the size of a Roth conversion or the timing of a sale, a CPA or financial adviser can model your own numbers.